Circuit breaker



Sept. 26, 1944. J w MAY AL 2,359,139

CIRCUIT BREAKER Filed Oct. 21, 1941 4 Sheets-Sheet l WITNESSES:INVENTORS Z4 John W May and TU Q Lindsfrom.

ATTORNEY Sept. 26, 1944. w, M EI-AL 2,359,139

CIRCUIT BREAKER Filed 001:. 21, 1941 4 Sheets-Sheet 2 Eimefal WITNESSES:

Tyre Lindsfrom ATTORN Sept. 26, 1944. J. w. MAY EIAL 2,359,139

CIRCUIT BREAKER Filed Oct. 21, 1941 4 Sheets-Sheet s J0]??? 14/ May andTare Lina 51mm.

BY W A'TTokN Patented Sept. 26, 1944 2,359,139 cnwurr BREAKER John W.May, Pittsburgh, and Ture Lindstrom,

Edgewood. Pa., assignors to Westinghouse Electric 8: ManufacturingCompany, East Pittsburgh, Pm, a corporation of Pennsylvania ApplicationOctober 21, 1941, Serial No. 415,924

18 Claims.

This invention relates to circuit interrupters, and more particularly tocircuit breakers of the type which are automatically operated inresponse to overload currents in the circuit controlled by the breaker.

One object of the invention is to provide a cir cult breaker with animproved device of simple and inexpensive construction, which isoperable to cause the breaker to automatically open its contacts inresponse tooverloads in the circuits.

Another object of the invention is the provision of an improved circuitbreaker which is capable of being tripped by the application of arelatively light tripping force by the electroresponsive trip means.

Another object of the invention is the provision of a circuit breakerhaving a novel trip device comprising a spring means in which energy isstored by the closing movement of the breaker and which is released by alatch to cause automatic opening of the breaker mechanism in response topredetermined overload conditions in the circuit.

Another object of the invention is the provision of a circuit breakerhaving a novel tripping means comprising a spring means connectedbetween a tripping element and a part movable with the movable contactassembly, the tripping element being normally held in inoperativeposition by a latch which is adapted to be released in response toabnormal current conditions in the circuit.

Another object of the invention is the provision of a circuit breaker aspreviously described wherein the opening movement of the breaker actsthrough the tripping spring to reset the tripping element to latchedposition.

Another object of the invention is the provision of a circuit breaker aspreviously described wherein the spring means for tripping the breakerand for resetting the trip device also serves to permit overtravel ofthe parts to which the spring is connected in both directions ofoperation.

Another object of the invention is to provide a circuit breaker havingan improved trip mechanism which is reset automatically when thecontacts are opened.

Another object of the invention is to provide a circuit breaker whereinthe movement of the operating mechanism to open the contacts resets thetrip device.

Another object of the invention is to provide a circuit breaker with anovel spring device which is normally under tension to efiect trippingStill another object of the invention is to pro.-

vide a circuit breaker with a novel linkage operable in one direction totrip the breaker and operable in another direction to reset the tripdevice.

The novel features that are considered characteristic of the inventionare set forth in particular in the appended claims. The inventionitself, however, both as to structure and operation, together withadditional objects and advantages thereof, will be best understood fromthe following description of one embodiment thereof when read inconjunction with the accompanying drawings, in which:

Figure 1 is a vertical sectional view through the center pole of athree-pole circuit breaker embodying the features of the invention;

Fig. 2 is a horizontal sectional view on an enlarged scale takensubstantially on line 11-11 of Fig. l, and showing the trip device ofthe breaker;

Fig. 3 is a fragmentary view showing the contact arm for the outer polesof the breaker;

Fig. 4 is an enlarged sectional view through the trip device for thecenter pole taken substantially on line IV--IV of Fig. 2, and showingthe trip device just after the breaker has been tripped by the bimetaltrip element, but before the contacts have opened;

Fig. 5 is an enlarged sectional view similar to Fig. 4, but showing theparts of the trip mechanism in the positions assumed after the breakerhas been tripped by the bimetal trip element and after the contact armhas moved to open the contacts, but before the bimetal trip element hascooled;

Fig. 6 is an enlarged sectional view through the resilient linkageconnecting the trip lever to the contact arm; and

Fig. '7 is a fragmentary view, partly in section, taken on line VII-VIIof Fig. 4, showing the construction of a part of the trip device.

Referring particularly to Figs. 1 and 2 of the drawings, the circuitbreaker, which is of the multi-pole type, is mounted on a base ll ofmolded insulating material. Secured to the base II is a frame structurecomprising a pair of substantially parallel side franes I1rigldlyconnected adjacent the base I! by a cross-frame I9, whereby theframe structure is secured to the central part of the base II throughthe agency of bolts 2| and 23. The side frames I1 are Joined at theirouter ends by cross-members 25 and 29 to form a rigid framework. Thebreaker mechanism may be enclosed in'a-casing, indicated by dot and dashlines at I3, which may be suitably secured to the base II.

A contact arm 39 for the center pole of the breaker is provided with apair of spaced arms 3| pivotally mounted on a rod 29 supported by theside frames I1 (see also Fig. 2). The arms 3| are rigidly connected by across-bar 32 adjacent the pivot 29. At its free end, the contact arm 39for the center pole is provided with spaced projections 33, and amovable contact member 35 is pivotally mounted on a pivot pin 31supported in the projections 33.

A movable contact 39 secured on the contact member 35 cooperates with astationary contact 49 mounted on a conductor 4| secured to the base I Iby bolts 43. The conductor 4| is bent at right angles and projectsthrough the base II where it forms a terminal 45.

Contact pressure is provided by a spring 93 surrounding a. rod 5|pivotally connected to the contact member 35. The rod 6| slidablyprojects through an opening in a projection 59 on the contact arm 39,and the spring 63 is compressed between this projection and a washer 65secured to the rod 6|.

The circuit breaker of the instant invention is of the multi-pole type,and each pole is provided with a stationary contact and a correspondingmovable contact similar to the contacts of the center pole. However,only the center pole is provided with a contact arm 39 supported bypivoted arms 3|. A tie-bar 61 surrounded by a sheath 69 of insulatingmaterial is securely clamped in the arm 39 by means of a split clamp 19and a bolt 1|. The tie-bar 61 extends across all of the poles of thebreaker, and has brackets 13 (Fig. 3) clamped thereon by means of aclamp 11 and a bolt 18, there being a bracket 13 associated with each ofthe outer poles of the breaker. The insulating sheath 69 between thetie-bar and the clamps 19 aand 11 insulates the three movable contacts35 from the tie-bar. Each of the brackets 13 for the outer poles isprovided with spaced projections 33 which pivotally support a contactmember 35. This contact member is the same as the contact memberdescribed in connection with the description of the contacts for thecenter pole, and like parts have been given the same referencecharacters. The contact members 35 for the outer poles are pivoted onpivot pins 31 and are provided with contact pressure springs 63. Thestationary contact and terminal for each of the outer poles is identicalto that of the center pole previously described.

Since the brackets 13 which carry the outer contact members 35 aremounted on the tie-bar 61, which is securely clamped in the contact arm39 (Fig. 1) for the center pole, it is clear that operation of thecontact arm 39 will simultaneously operate the contacts for all of thepoles of the breaker.

When the contact arm 39 is rotated clockwise to open the contacts, thesprings 53 cause the contact members 35 to rotate in a counter-clockwisedirection about their pivot pins 31 so that only the tip portions of themovable contacts engage the stationary contact members 4| prior toseparation of the contacts. Continued clockwise movement of the contactarm 39 causes nuts 15 on the rods II to strike the projections 59 andthus limit the movement of the contact members 35 relative to thecontact arm 39, and the three movable contacts are then moved to openposition with the contact arm 39.

The are incident to the rupture of the circuit is extinguished by an arcextinguisher 13, one being provided for each pole. Such arcextinguishers are well known in the art and comprise, generally, a stackof slotted plates disposed adjacent the path of movement of each contactmember 35. The plates of the extinguisher draw the arc toward the endsof the slots,

which results in breaking up the arc into a plurality of short arcs andcauses said arcs to be cooled and extinguished.

The electrical circuits for the several poles of the breaker areessentially the same, each circuit extending from the terminal 45through the conductor 4|, contacts 49 and 39, the contact member 35, aflexible shunt conductor 19, a connector 21 of conducting material, aconducton 9|, a connector 49 to which one end of the conductor 8| issecured by a screw 5|, to a terminal conductor 53 secured to the base IIby a pair of bolts 55, one of which serves to secure the connector 49 tothe conductor 53. The conducting member 21 of the center pole is securedto the cross piece I9 of the frame by the bolt 23, and the conductingmembers 21 of the outer poles are bolted to the base II with a spacerbetween the base and each member to align the outer conducting membera'21 with the corresponding element 21 of the centerpole. The terminals45 and 53 of each pole serve to connect the breaker in an electricalcircuit.

The contact arm 39, together with the tie-bar 91, is biased in aclockwise direction toward open contact position by a pair of springs(only one being shown) having one end anchored on a fixed pivot 31 inthe frames I1, and the other end connected to a projection 88 on the arm39. In the closed position of the breaker, the contact arm 39 isreleasably restrained in closed contact position (Fig. 1) by means of alinkage and toggle mechanism, including a lever 89 comprising a pair oflevers rigidly connected by a crossmember 1 and pivotaliy supported on apivot 9| mounted on the main frame I1. A main operating togglecomprising links 93 and 95 oneratively connects the lever 89 and thecontact arm 39. The link 93 is pivoted on a pivot I9I in the lever 89,and the toggle links 93 and 35 are pivotally connected by a knee pin 91.The link 95 is pivoted on a pivot pin 99 supported between the arms 3|of the contact arm 39. The link 95 comprises a pair of links joined by across-bar I I5, which cooperates with an extension of the link 93 tolimit upward movement of the main operating toggle.

A link I93 connects the lever 39 to one arm of a lever I95 pivoted onthe fixed pivot 81. The other arm of the lever I95 is pivotallyconnected to one end of a toggle link I91 having its other end pivotedto a toggle link I 99 by a knee pin III. The toggle link I99 is pivotedon a fixed pivot I I3 supported in the frame I1. The link I91 comprisesa pair of links rigidly connected by a yoke II9, which is provided'witha projection bent outwardly therefrom, to which projection is secured anextension Hi. The purpose of the extension I2| is to cooperate withmanually operable means to trip the breaker, as will be described later.The link I03 and the lever I05 each comprises a pair of parallel membersjoined by a yoke substantially as illustrated. The

toggle link I09 comprises a pair of links rigidly connected at theirends adjacent the fixed pivot II3 by a cross-member I23 having formedproiections I24 and I21 thereon.

The linkage just described serves to releasably hold the contact arm andconsequently the contacts in the closed position. In the closedposition, the main operating toggle 9395 is over center above a lineconnecting the centers of the pins 39 and IN, the overcenter position ofthe toggle being limited by the end of the link 33 engaging thecross-member II5 on the link 95. With the toggle 93-95 in its overcenterposition, the force exerted by the springs 85, acting through thecontact arm 30 and the toggle 93-35, biases the lever 89 in a clockwisedirection. The tripping toggle I01-I09 is biased over center to the leftof a line drawn through the center of the fixed pivot H3 and the pointof connection of the link I01 with the lever I05, by a spring I28tensioned between the yoke H9 and the fixed pivot II3. The overcentermovement of the toggle I01-I09 i limited by the projection I24 strikingan adjustable screw I22 in the cross-member 25 of the frame. The toggleI01I 03 in its overcenter position, acting through the lever I05 andlink I03, prevents clockwise rotation of the lever 09 and consequentlyholds the contact arm 30 in its closed contact position.

The tripping toggle I01-I03 is adapted to be moved to collapsed positionto cause opening of the contacts by a trip device indicated generally atI33 (Figs. 1, 4 and 5) acting through a trip rod I35 slidably mounted ina bracket I38 secured to the frame I1. The trip device, when actuated inresponse to an overload current, thrusts the rod I35 upwardly. Duringits upward movement, the rod I35 strikes the formed portion I21 of thecross-member I23 of the tripping toggle link I09, and rocks said linkclockwise about its fixed pivot II3, causing collapse of the trippingtoggle I'I-I09 and linkage 99- I03-I05.

Collapse of the tripping toggle I01-I09 permits the springs 85 to rockthe contact arm 30 in a clockwise direction to open the contacts. Themain operating toggle 93-35'does not immediately collapse, but moves asa unitary linkage to transmit the movement of the contact arm to thelever 89, rocking this lever clockwise, and through the link I03 rocksthe lever I also in a clockwise direction to complete the collapse ofthe tripping toggle I01I 09.

The clockwise or opening movement of the contact arm 30 is arrested bythe tie-bar 61 striking a portion I31 of the frame I1, and at this timedue to the momentum of the toggle 33-35, including the comparativelyheavy cross-bar II5, the main toggle 93-35 is caused to move over centerin a direction to cause its collapse. By the time the knee pin 31 of themain toggle has passed below the center line 99-IOI, the weight of thelinkage and parts causes the main togcenter position and in restoringthe lever I05, link I03 and lever 89 to their normal position. The maintoggle 93-95 remains in its collapsed condition until the contacts arereclosed.

In order to'manually close the contacts, a manually operable handle MIis provided. This handle is secured on the outer end of a short shaftI42 rotatably supported in a bracket I43 of insulating material. Thebracket I43 is secured by screws I44 and I48, respectively, to thecrossmembers 25 and 26 of the frame I1. The free end of a crank arm I50,secured to the shaft I42 adjacent the bracket I43, is bifurcated andpivotally carries a downwardly extending link I5I. The lower end of thelink I5I is notched and engages an hourglass-shaped roller I53 rotatablymounted on a cross-bar I41 rigidly connecting the outer ends of a pairof levers I45 pivotally supported on the shaft or fixed pivot 9|. Neartheir innerends, the levers I45 are rigidly connected by a cross-barI43. The levers I45 and the crossbars I41 and I49 form a closing leverpivoted at 9I, the levers I45 being spaced apart and disposed on theoutside of the frame I1. Projections I52 on the cross-bar I49 havemounted therein a pivot I51, upon which is rotatably mounted a rollerI55.

Rotation of the handle MI in a clockwise or closing direction, indicatedby the arrow (Fig. 1), thrusts the link I5I downwardly and, due to thecooperation of the link with the roller I53, rocks the closing lever I45in a clockwise direction. During this movement, the roller I55 engagesthe link 93 of the now collapsed toggle 93-95 and moves said toggle toits overcenter position. Since at this time the toggle I01--I09 is overcenter in its restraining position, the lever 83 is prevented frommoving. Consequently, the force applied to straighten the toggle 9395rotates the contact arm 30 in a counterclockwise direction to close thecontacts and tension the springs 85. The clockwise movement of theclosing lever I45 and the roller I55 is sufficient to carry the toggle9395 over center above the line 33-IOI, so that the contacts are held intheir closed position until the breaker is again tripped.

As soon as the contacts are closed and the toggle 9335 is moved to itsovercenter position, the handle I4 may be released, whereupon a springI53 tensioned between a projection on the frame I1 and the closing leverI45 rocks the closing lever counterclockwise, thrusting the link I5Iupwardly and rotating the handle to its neutral position (Fig. 1). Thecounterclockwise rotation of the lever I 45 is limited by the cross-barI49 striking a stop I48 in the bracket I38.

The contacts 33-40 may be closed (and the trip device I33 reset)automatically by means of an electric motor I25 mountedon a plate I26(see Fig. 2) secured to the side of the frame I1. The motor I25 may beenergized from any suitable source and in a manner well known in theart, and when so energized it is adapted, through suitable drivingconnections, to rotate a crank disc I29 which carries an anti-frictionroller I30. An arm I3I secured to the side of the closing lever I45 isprovided with a cam surface I32 nor- 138.011) disposed in the path ofrotation of the roller When the crank disc I29 is rotated, uponenergization of the motor I25, the anti-friction roller I30 engages thecam surface I32 and rotates the arm I3I, and consequently the closinglever I 45 clockwise, straightening the toggle 93-95, in the mannerpreviously described, to close the contacts. As soon as the roller I30passes out of engagement with the arm I3I, the spring I69 acts torestore the closing lever I46'to its normal, unoperated position (Fig.1). The motor I26 is deenergized by a suitable limit switch (not shown).

The breaker may be tripped manually by rotating the handle Ill through asmall angle in a counterclockwise direction from its neutral position.Rotation of the handle in tripping direction causes a projection I6I(Fig, 1) on the link Iil to engage the previously described extensionIII on the yoke II9 of the toggle link I01, and move the tripping toggleI01I09 over center in a direction to cause its.collapse. This permitsthe springs 86 to open the contacts, as was previously described.Reclosing the contacts is eil'ected in the previously described manner.

The trip device I33 is removably supported on the circuit breaker toprovide for interchanging of trip devices having different trippingcharacteristics. The trip device is mounted on a framework includin aU-shaped bracket I63 (Figs. 1, 2, 4 and secured to the center poleconnector 21 by means of the screw 28, which secures the conductor 8|thereto. The bracket I63 has a pair of upwardly bent side members I65(see Fig. 2) and a portion I61 (Fig. 4) to the underside of whichportion I61 is secured a plate I69 of insulating material. Mounted onthe plate I69 is a frame "I also of molded insulating material. Anangular flange I13 (Fig. 2) molded integral with the frame I1I issecured to the plate I69 by screws I15.

The trip device I33 comprises a thermally responsive bimetal elementoperable on overloads below a predetermined value, and an electromagnetoperable on overloads above the predetermined value, there being onebimetal element and one electromagnet for each of the three poles of thebreaker. The conductor 8I previously mentioned extends downwardly fromthe connector 21, and is bent at right angles and extends to the right(F18. 5) along the bottom face of the plate I69 for a predetermineddistance where it is bent back upon itself. ductor strip is made ofreduced width to provide an increased resistance portion so that itserves as a heater for the bimetal element. Just to the left of theplate I69, the conductor 8| is again bent toward the right and thendownwardly to the connector 49,

The upper leg of the loop of the conductor BI is secured to the plateI69 by a rivet I11 (Figs. 4 and 5), and the reversely bent portion ofthe loop is secured to a bimetal element I19 and to a bracket I8I (seealso Fig. '7). The downwardly extending leg of the conductor 8| passesbetween the legs of a U-shaped magnet core I83, which, together with thebracket I8I, is securely attached to projections I85 and I81 (Fig. 7)

of the frame I69 by means of rivets I89. A block I9I of insulatingmaterial is inserted between the legs of the loop of the conductor 8| toseparate the legs and to form a substantially rigid structure.

Overload currents traversing the circuit of any pole of the breaker, andconsequently the conductor 8I of any pole, serve to heat thebimetal I19of the affected pole and to energize the corresponding magnet core I83.

A movable armature I93 is secured on the end of a rod I95 slidablymounted in an opening in a downwardly extending portion I91 of thebracket I8I. A spring I99 compressed between a shoulder on the rod I95and the bracket This looped portion of the con- I 9| maintains thearmature I93 in open air gap position (Figs. 1 and 4), and returns thearmature to this position from its attracted position. The right-handend (as viewed in Figs. 1, 4 and 5) of the rod I96 is provided with ahead 2M which engages a U-shaped notch molded in a tripbar 203. The tripbar is of molded insulating material, and has a metal member 266 moldedtherein at each end. The members 266 (only one of which is shown) arepivotally supported on spaced brackets 201 secured to and depending fromthe plate I69, and serve to \pivotally support the trip bar. At theirlower ends, the brackets 201 support a cover 209 of insulating materialheld in place by screws 2i I. The trip bar 203 is biased to its latchingposition (Fig. 1) by a spring 2I3 (Figs. 4 and 5) compressed between aprojection 2I5 of the trip bar and the plate I69.

Only one trip device I33 has been described. However, it is to beunderstood that a plurality of trip devices are provided, one for eachof at least two poles of the breaker, all of which are mounted on theplate I69 substantially as illustrated and described. Each of the tripdevices is operable in response to overload conditions in the fcilcllitof their corresponding poles to rotate the trip bar 293 in trippingdirection to trip the breaker, the trip bar extending across all of thepoles of the breaker.

Attached to the trip bar 203 is a latch member 2I1 provided with a latchprojection 2I9 and a limit projection 22I. The latch member 2I1 isadapted to engage the end of a latch arm 223 pivotally supported on ashort shaft 226 mounted in the side members I of the U-shaped bracketI63. The latch arm 223 is provided with a yoke 221, one end of whichforms an arm 223 (Fig. 2) bearing on the shaft 225. A spring 23I iscoiled about the shaft 225 and disposed to bias the latch arm 223 in acounterclockwise direction (Fig. 1) toward its latched up position.

A pair of locating members 233 is rigidly supported on a rod 235,mounted in the frame I1, and on the shaft 29. Each of the members 233 isprovided with a open slot embracing the shaft 225 to aid in locating thetrip device I33 when it is installed in the breaker, and to assist insupporting the trip device after it is installed. The members 233 arespaced apart by a spacer 231 surrounding the rod 235 and a spacer 239.

The trip device I33 does not itself operate the trip rod I35 to trip thebreaker, but releasably restrains a tripping mechanism, indicatedgenerally at 240 (Fig. 5) in operative position. The tripping mechanism240, when released upon operation of the trip device I33, operates thetrip rod I35 to trip the breaker.

The trip mechanism 240 is mounted on a laterally extending bar 2 moldedintegral with the frame Hi. The bar I supports a bracket 243 comprisinga pair of parallel side plates 246 rigidly connected by a yoke 241,which yoke is secured to the bar MI by bolts 249. The upper ends of theplates 245 between them support a pivot shaft 25I, upon which ispivotally mounted a lever comprising a pair of arms 253, one of whichhas a downwardly projecting extension 255 engageable with the yoke 221of the latch arm 223. The arms 253 are rigidly joined by a yoke 259, andat their free ends carry a pivot pin 26I. A pair of links 263 pivoted onthe pin 26I are pivotally connected to spaced arms 266 'of a bell crankor trip member 261 by means of a pivot pin 269. The bell crank 261comprises the spaced arms 235 connected by a yoke 21!, the bell crankbeing pivotally supported on a pivot pin 212 mounted in the lower endsthe spaced plates 235. The other arm 213 of the bell crank 23! isintegral with one oi the arms 233 and has an ear 215 bent at rightangles to its free end. An adjustable screw 21! is mounted in 'the ear215, and is locked in position by a lock nut 219.

When the trip mechanism 240 is operated, as will be described later, thebell crank 23! is rocked counterclockwise, and the screw 21! strikes thelower end of the previously described tri rod I35 to effect tripping oithe breaker.

The point of connection 23! of the links 253 and 233 is connected to thearms 3! of the contact arm 30 by means of a resilient linkage indicatedgenerally at 23! (Figs. 1, 4, and 6). Referring particularly to Fig. 6,the resilient linkage 23! comprises a cylinder 233, pivotally mounted ona rod 235 which extends through a transverse opening in the cylinder andthrough suitable openings in the arms 3! of the contact arm 33, a rod23! pivotally supported on the pin 23!, and a compression spring 239compressed between washers 29! and 293 in the cylinder. The washer 29!is adapted to engage the inner end of a cylindrical sleeve 295 mountedin the cylinder 233 and held in place by the rod 235 passingtherethrough. The sleeve 295 acts as a 'limit stop to limit theexpansion of the spring 239; the washer 293 engaging the inwardlyflanged end 291 01 the cylinder 233 serves the same purpose. A spacer299 (Fig. 4) surrounding the rod 285 spaces the linkage 23! adjacent oneof the arms 3! and maintains it in alignment with the linkage 253233.

. In the normal untripped condition, the flexible linkage 23! is undertension, that is, the rod 23'I-is slightly drawn out of the cylinder233, giving a greater compression to the spring 239 than obtains withthe parts in the positions shown in Fig. 6. The force of the spring 239is applied to the pin 26! and biases the lever 253 and the bell crank23! in a counterclockwise or tripping direction. Movement of the lever253 and bell crank 23! is normally prevented by engagement of theprojection 255 with yoke 22'! of the latch arm 223, which is normallylatched up by the latch member 2 I9 (see Fig. 1).

Upon the occurrence of a persistent overload current below apredetermined value in the circuit of any one of the poles of thebreaker, the current flowing through the corresponding con ductor 3!heats the bimetal element I19 and causes it to flex in a downwarddirection. The free end of the bimetal engages an adjusting screw 33!held in place in the trip bar 233 by a lock nut 303 and rocks the tripbar clockwise to unlatch the latch am 223. As soon as this occurs, thelinkage 23! contracts, due to the expansion of the spring 239 (Fig. 6)within the cylinder 233, rocking the lever 253 counterclockwise. Thiscauses the toggle comprising the lever 253 and link 253 to move furtherabove the center line 25I-239, and rocks the bell crank lever 23!counterclockwise to trip the breaker through the agency of the trip rodI35.

The parts just described are shown in Fig.4 in this position, that is,an instant after the breaker is tripped, but before the contacts haveopened.

Operation of the trip rod, as previously described, causes collapse ofthe linkage 93, 95, 39, I33, I35, I3! and I09 (Fig. 1) which permits thespring 35 to rotate the contact arm 33 to open the contacts. As thecontact arm 33 rotates clockwise in opening direction, the action of thelinkage 23! (Fig. 5) is reversed, and the cylinder 233 moves with thecontact arm 33,, and, acting through the washer 29!, the spring 239 andthe washer 293, which at this time is in engagement with a shoulder onthe rod 231, thrusts the rod 23'! in a direction to straighten thetoggle 253-433. This simultaneously accomplishes two things. Actingthrough the link 233, the bell crank lever or trip member 23'! is rockedclockwise to its normal position to permit restoration of the trip rodto its normal position, which permits resetting of the linkage 39, I33,I35, I31 and I39 (Fig. 1). The straightening of the toggle 253233 alsorocks the lever 253 clockwise,

whereupon the spring 23! rotates the latch arm 223 counterclockwiseslightly beyond latching position, this movement of the arm 223 beinglimited by a projection 305 on the bracket I33.

As the bimetal I19 cools and resumes its normal shape (Fig. 1), thespring 2I3 rotates the trip bar 203 counterclockwise to latchingposition with the projecting latch 2! 9 in the path of clockwisemovement or the latch arm 223. The

' counterclockwise movement of the trip bar 233 is limited by theprojection 22! thereon strikin the arcuate end of the latch arm 223.

Now when the contact arm 33 is rotated in a counterclockwise or closingdirection, upon proper operation of the handle Ill, or energization ofthe motor I25, to close the contacts, the linkage 23! moves therewith,rocking the lever 253 counterclockwise a slight amount and through theprojection 255 rocks the latch arm 223 clockwise a slight amount untilit is arrested by engagement with the latch2! 9 thus restraining thelatch arm and the toggle 253233 in latched position. This also arreststhe counterclockwise movement of the lever 253. Continued closingmovement or the contact arm 33 again places the linkage 23! in tension,i.e., stores energy in the spring 239, in readiness for a succeedingtripping operation.

The circuit breaker is tripped instantaneously on overloads in thecircuit through any of the poles exceeding a predetermined value; forinstance, exceeding approximately ten times normal rated current. Uponthe occurrence of an overload above the predetermined value, or a shortcircuit, the current flowing through the corresponding conductor 3!energizes the magnet core I33, which immediately attracts the armatureI93. The armature draws the rod I toward the left (Fig. 5), the head 23!of said rod acting to rock the trip bar 233 in unlatching direction.When the trip bar 233 has unlatched the latch arm 223, the partsfunction to trip the breaker in the previously described manner. As soonas the contacts are opened and the circuit ruptured, the spring I99returns the armature I93 and rod I95 to unattracted position, and thespring 2I3 rocks the trip bar 233 to latching position. The tripmechanism is rest upon movement of the contact arm 33 to open position,and the contacts reclosed as previously described.

The breaker is trip-free under all conditions. Should the handle Ill beheld in its closed position against an overload current, holding theroller I55 against the toggle link 93, the contacts will open, sincecollapse of the linkage 39, I03, I35 and !3'I-I39 permits the toggle93-95 to move in opening direction as a unitary linkage. When theclockwise movement of the contact arm 30 is arrested by the frame II,the force of the spring 85 is no longer applied to the toggle 93-95, andthe linkage, consequently when the handle Ill is released and theclosing lever H rotated to normal position, the weight of the linkageacts to move the toggle 93-45 over center-to collapsed position andreset the linkage 89, I03, I05 and NIL-I09. The contacts may now beclosed in the previously described manner.

From the foregoing description it will be seen that the parts are soarranged that a very light load is applied to the latch member andtherefore requires the application of a relatively light force by thecurrent responsive trip device to unlatch the trip mechanism, the actualwork 01' tripping the breaker mechanism being performed by the springlink. A further advantage resides in the provision of the resilientconnection or linkage which operates in one direction to trip thebreaker and is operable in another direction, upon opening of thecontacts, to automatically restore the latch member to latching positionwithout the necessity of preliminary manipulation of the closingmechanism. The resilient connection also permits operation of themechanism without strain or breakage since it permits overtravel oi theparts in both directions.

Having described the preferred embodiment of the invention in accordancewith the patent statutes, it is to be understood that various changesand modifications may be made in the structural details disclosedwithout departing from some of the essential features of the invention.It is, therefore, desired that the language of the appended claims begiven as reasonably broad interpretation as the prior art permits.

We claim as our invention:

1. In a circuit breaker, relatively movable contacts, operatingmechanism for said contacts including closing means for closing saidcontacts, means operatively relating said closing means and said movablecontacts, a trip mechanism including a toggle independent of saidrelating means, said toggle being biased in a direction to cause openingof the contacts, latch means for releasably restraining the tripmechanism, and a current-responsive trip device operable in response tooverload circuit conditions to cause said latch to release the toggleand permit operation of the trip mechanism, said toggle being operableby the operating mechanism when the contacts are opened to permitrelatching of the latch means.

2. In a circuit breaker, relatively movable contacts, operatingmechanism for said contacts, a normally latched trip mechanism having alinkage including a compression spring biased to cause opening of thecontacts, a current-responsive trip device operable to unlatch the tripmechanism, said operating mechanism acting through said linkage to resetthe trip mechanism when said operating mechanism moves to open the.contacts.

3. In a circuit breaker. relatively movable contacts, operatingmechanism operable to open and close the contacts, a releasable tripmember operable to cause opening of the contacts, a linkage including acompression spring biasing said trip member in tripping direction, and acurrent-responsive trip device operable in'response to overload circuitsto release the trip member, said operating mechanism acting through saidlinkage upon opening oi the contacts to cause resetting 01 parts of saidcurrent-responsive trip device.

trip mechanism including a toggle operable to enfect opening of thecontacts. a spring means biasing said toggle in tripping direction atleast when said contacts are closed, and a current-responsive tripdevice operable to cause operation or said toggle upon the occurrence ofan overload, said spring means being operable by the operating mechanismupon opening 01' the contacts to reset the toggle and topermit-resetting 01 parts or said trip device.

5. In a circuit breaker, relatively movable contacts, a switch membermovable to open and to close said contacts, actuating mechanism formoving said switch member to open and to closed circuit positions, atrip mechanism including a linkage biased to cause an opening operation0! the contacts, a latch for latching the trip mechanism in operativeposition, and a current-responsive trip device operable to unlatch thetrip mechanism upon the occurrence oi an overload, said switch memberacting through said linkage when said member is moved to open thecontacts to effect resetting of the trip mechanism.

6. In a circuit breaker, relatively movable contacts, actuatingmechanism for said contacts, a contact arm operable to open thecontacts, a trip member operable to cause said mechanism to open saidcontacts, a linkage including a spring for operating the trip member,means for releasably restraining said linkage and a current-responsivetrip device for releasing the linkage upon the occurrence of an overloadcurrent, said spring being operable by the contact arm upon opening ofth contacts to efl'ect resetting of the linkage.

7. In a circuit breaker, relatively movable contacts, operatingmechanism for said contacts, a contact arm operable to open thecontacts, a trip member, a toggle operatively connected to said trip'member, a resilient linkage connecting the toggle to the contact arm,said resilient linkage biasing the toggle in a direction to operate thetrip member at least when said contacts are closed, a current-responsivetrip device operable in response to predetermined circuit conditions tocause operation of the trip member, said resilient linkage beingoperable by the contact arm when said arm is operated to open thecontacts to reset the trip member and permit resetting oi the tripdevice.

8. In a circuit breaker, relatively movable contacts, operatingmechanism for said contacts, a contact arm operable to open thecontacts, a trip member operable to cause opening of the contacts, atoggle operatively connected to said trip member, a resilient linkageconnecting the toggle to the contact arm, said linkage biasing the tripmember in tripping direction at least when said contacts are closed, anda trip device responsive to overload circuit conditions to causeoperation of the resilient linkage, said linkage being operable by thecontact arm upon opening of the contacts to reset the toggle and tripmember.

9. In a circuit breaker, relatively movable contacts, operatingmechanism for said contacts, a

trip member operable to cause opening of the contacts, a releasablelinkage biasing the trip member in tripping direction at least when saidcontacts are closed, means for releasably restraining said linkage, andan electroresponsive trip device responsive to overload current torelease said linkage, said linkage being operable by the operatingmechanism upon opening of the contacts to reset the trip member andpermit resetting or the'electroresponsive trip device.

10. In a circuit breaker, relatively movable contacts, operatingmechanism for said contacts, a trip member operable to cause saidmechanism to open th contacts, a linkage comprising a member connectedto the operating mechanism, a reciprocable member cooperating with saidmember and connected to said trip member, and resilient means betweenthe member and said reciprocable member, said linkage being operable tocause operation or the trip member, currentresponsive trip meansresponsive to overload currents to cause said linkage to operate thetrip member, said linkage being operable by the operating mechanism whenthe contacts are opened to reset the trip member.

11. In a circuit breaker, relatively movable contacts, a switch membermovable to open and to close said contacts, operating mechanism for saidcontacts, a trip member operable to cause opening of the contacts, atoggle operatively connected to the trip member, a linkage including apair or cooperating members one of which is connected to the switchmember the other being connected to the toggle, and aspring cooperatingwith said linkage, said spring biasing the trip' member in trippingdirection at least when said contacts are closed, a latch normallyrestraining the toggle to thereby restrain said trip member,

and a current-responsive trip device operable in response topredetermined circuit conditions to cause said latch to release thetoggle.

12. In a circuit breaker, relatively movable contacts, operatingmechanism for said contacts including closing means for said contacts,means operatively relating said closing means to said movable contacts,releasable trip mechanism including a toggle independent of saidrelating means and operable to cause opening of the con-,

tacts, a resilient linkage biasing said toggle in tripping direction, alatch for releasably restraining said toggle, and a current-responsivetrip device operable in response to predetermined circuit conditions torelease the trip mechanism, said toggle being reset to operativeposition by opening of the contacts.

13. In a circuit breaker, relatively movable contacts, operatingmechanism for said contacts,

a trip mechanism including a toggle movable to cause opening of thecontacts, latch means to releasably restrain the toggle, meansconnecting the toggle to a part movable with the operating mechanism,said connecting means including a spring operable when the toggle isreleased to move the toggle to thereby cause opening of the contacts, acurrent-responsive trip device operable to cause release of the toggle,said connecting means being operable by the operating mechanism when thecontacts are opened to restore the toggle to latching position.

14. In a circuit breaker, the combination of relatively movablecontacts, operating mechanism for said contacts, a pivoted trip memberoperable to cause opening of the contacts, a linkage comprising a pairoi cooperating members one of said members being operatively related tothe trip member. and the other member being connected to the operatingmechanism, and a spring associated with said cooperating members to biasthe trip member in tripping direction at least when the contacts areclosed, said. spring acting when released to operate the trip member,latch means to releasably restrain the linkage, and a current-responsivetrip device to operate the latch and'release the spring, said linkagebeing operable by. the operating mechanism acting through the spring toreset the trip member.

15. In a circuit breaker, the combination of relatively movablecontacts, operating mecha. nism for said contacts, a contact memberoperable to open-the contacts, a trip member operable to cause openingof the contacts, a toggle operatively connected to the trip member, saidtoggle being biased in tripping direction, means for operativelyconnecting the toggle and the contact member, said connecting meanscomprising a member connected to the contact member, a member connectedto the toggle, and a spring associated with said members, latch meansfor releasably restraining the toggle, and a currentresponsive tripdevice operable in response to overload circuit condition to release thetoggle, said connecting means acting to transmit the movement of thecontact members when the contacts are opened to reset the toggle.

16. A circuit breaker comprising relatively movable contacts, operatingmechanism for said contacts, means comprising a resilient linkageincluding a compression spring connected to a part movable with themovable contact, said spring being compressed when said contacts areclosed and being operable to cause an operation of the operatingmechanism to open said contacts, means for releasably holding saidspring in compressed condition, and current responsive means operable inresponse to predetermined overload conditions in the circuit for causingsaid holding means to permit operation of said linkage, the movement ofsaid contacts to open position acting through said linkage to reset saidholding means to holding position.

17. A circuit break r comprising relatively movable contacts, a membermovable in accordance with the movement of said contacts, operatingmechanism for said contacts, tripping means including a toggle, a springconnecting said member to said toggle and stressed when said contactsare closed, said toggle being operable to cause said operating mechanismto open said contacts, means for holding said spring in stressedcondition, and a trip device operable in response to overload currentsin the circuit to cause said holding means to permit the spring tooperate said toggle, said movable member acting when the contacts opento reset the toggle.

18. A circuit breaker comprising relatively movable contacts, operatingmechanism for said contacts, a switch member operable to open thcontacts, a trip member operable to cause opening of the contacts, aresilient linkage connecting the switch member to said trip member, saidresilient linkage biasing the trip member in tripping direction at leastwhen the contacts are closed and acting when released to operate thetrip member, latch means for releasably restraining the trip member, anda current-responsive trip device operable in response to overloadcircuit conditions to release the trip member, said resilient linkagebeing moved by the opening movement of said switch member to reset thetrip member.

JOHN W. MAY.

TURE LINDSTROM.

